判断是否为模拟器

 #define isSimulator (NSNotFound != [[[UIDevice currentDevice] model] rangeOfString:@"Simulator"].location)
    if (isSimulator) {
        if ([[UIScreen mainScreen] bounds].size.height > 700) {
            core.device = 2;
        }else{
            core.device = 4;
        }
    }

tableView.separatorStyle = UITableViewCellSeparatorStyleNone; 



- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
   
    CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);
    CGContextFillRect(context, rect);
   
    //上分割线，
    CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
    CGContextStrokeRect(context, CGRectMake(5, -1, rect.size.width, 1));
   
    //下分割线
    CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
    CGContextStrokeRect(context, CGRectMake(5, rect.size.height-1, rect.size.width , 1));
}

//使用系统自带的函数把json格式的字符串转换成 NSDictionary 然后再依次解析
NSDictionary *jsonDictionary = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&jsonParseError];

NSString

  NSString *test = @"111111"
        @"2222”;

test  ==  1111112222

http://code4app.com/ios/Spotlight-like-Hint-View/4f9cba5106f6e7a71f000004

oc 反射

   int i;
        int propertyCount = 0;
        objc_property_t *propertyList = class_copyPropertyList([/*NSMutableArray*/** class], &propertyCount);
        
        for ( i=0; i < propertyCount; i++ ) {
            objc_property_t *thisProperty = propertyList + i;
            const char* propertyName = property_getName(*thisProperty);
            NSLog(@"Person has a property: ‘%s‘", propertyName);
        }

方法省略参数

@interface NSMutableArray (variadicMethodExample)

- (void) appendObjects:(id) firstObject, ...;  // This method takes a nil-terminated list of objects.

@end

@implementation NSMutableArray (variadicMethodExample)
- (void) appendObjects:(id) firstObject, ...
{
    id eachObject;
    va_list argumentList;
    if (firstObject)                      // The first argument isn‘t part of the varargs list,
    {                                   // so we‘ll handle it separately.
        [self addObject: firstObject];
        va_start(argumentList, firstObject);          // Start scanning for arguments after firstObject.
        while (eachObject = va_arg(argumentList, id)) // As many times as we can get an argument of type "id"
            [self addObject: eachObject];               // that isn‘t nil, add it to self‘s contents.
        va_end(argumentList);
    }
}
@end

显示完整的访问路径

defaults write com.apple.finder _FXShowPosixPathInTitle -bool TRUE;killall Finder


恢复默认状态

defaults delete com.apple.finder _FXShowPosixPathInTitle;killall Finder



输入想要去的文件夹路径
按键盘 Command + Shift + G



LAST SHUTDOWN

+ (instancetype)shareDb
{
    static STDbHandle *stdb;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        stdb = [[STDbHandle alloc] init];
    });
    return stdb;
}

Xcode文档代码注释工具vvDocumenter
插件下载：https://github.com/onevcat/VVDocumenter-Xcode
安装：运行下载的vvDocumenter工程,重启Xcode
使用：方法前面输入///，自动生成注释框架，修改对应说明

1. 试了Hide during application launch的勾选选项，不可以
2. 试了ViewController中用函数，还是不可以

xcode用Tab建立了多个子界面
操作方式：option+shift，然后点击要打开的文件，会出现以下选项~

NSRecursiveLock
 NSRecursiveLock类定义的锁可以在同一线程多次获得，而不会造成死锁。

一个递归锁会跟踪它被多少次成功获得了。每次成功的获得该锁都必须平衡调用锁住和解锁的操作。只有所有的锁住和解锁操作都平衡的时候，锁才真正被释放给其他线程获得。

NSFileManager

contents 内容
create    创建
remove  移动
copy      复制
handler 处理者
exists 存在
readable
writable
attributes

保存图片

- (void)downloadImageWithURL:(NSString *)url toSavePath:(NSString *)toSavePath{
   
    NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:url]];
    UIImage *image = [UIImage imageWithData:imageData];
    if (image != nil) {
        [UIImagePNGRepresentation(image)writeToFile:toSavePath atomically:YES];
    }
}

http://www.w3school.com.cn/sql/sql_distinct.asp